Although thermoplastic elastomers (TPE) have been around for quite some time, intensive research for biodegradable TPE just started recently and there are not many commercial elastomeric biodegradable materials in the market today. Biodegradable TPE have the potential uses as implantable devices because of their controllable elasticity and the possibility of changing their chemistry and structure. They also have potential applications in the biomedical area, especially in the area of controlled drug delivery and tissue engineering.
Generally, biodegradable TPE are in the form of A-B-A triblock copolymers with B as the so-called “soft segment” and A as the so-called “hard segment”. A-B-A triblock copolymers with ε-caprolactone (ε-CL or CL) as the B block and L-lactide (LA) as the A block have been done by Qian et al (Polymer Degradation and Stability 2000, 68(3), 423-429), but due to the crystallinity of ε-CL the triblock copolymers did not have any elasticity at all despite the good elongation results. Meanwhile, similar triblock copolymers but with trimethyl carbonate (TMC) as the B block have also been studied. With TMC being an amorphous middle block, the triblock copolymers were said to be elastic although no data was provided regarding their recovery properties. Random copolymers of ε-CL and TMC with interesting mechanical properties were synthesized, but not related to the thermoplastic elastomers synthesis. A-B-A triblock copolymers with ε-CL and TMC as amorphous central blocks and L-lactide as crystalline blocks have also been investigated by Kricheldorf and Rost (Macromolecules 2000, 33 (3), 795-800) but in order to get good mechanical properties, the triblock copolymers have to be transformed into multiblock copolymers by chain extension with 1,6-hexamethylenediisocyanate (HMDI), which toxicity is often questioned. Furthermore, only minimal mechanical properties testing were done to the triblock copolymers.
Therefore, there is a need to provide triblock copolymers having improved elastic properties as thermoplastic elastomers.